# Max Zs Values vs Grant TechBox

The clearest difference is price: Grant TechBox at Free against Max Zs Values's $9.99. Max Zs Values's advantage is update cadence (every 4 months vs every 12 months) and iOS requirement (11.0 vs 15.0). On ads, in-app purchases and device support there is nothing between them.

Grant TechBox is free to download; Max Zs Values costs $9.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Max Zs Values ships an update every 4 months, Grant TechBox every 12 months. The most recent releases landed on September 24, 2026 and September 3, 2026 respectively.

## The numbers

| Metric | Max Zs Values | Grant TechBox |
| --- | --- | --- |
| Price | $9.99 | **Free** |
| Positive reviews | 55.2% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 4 months** | Every 12 months |
| Monetization | Paid | — |
| Size | 15 MB | 47 MB |
| Requires iOS | **11.0** | 15.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Pro Certs Software Ltd](https://appshunter.io/developer/444429696) | [Grant Engineering UK LTD](https://appshunter.io/developer/1042420331) |

## What reviewers say

### Max Zs Values

[App page](https://appshunter.io/ios/app/max-zs-values/id498838137)

This app calculates and displays maximum permitted Zs values for electrical installations, adhering to the 18th Edition of BS 7671. It includes 80% temperature adjusted values and manufacturer charts for MCCB devices, along with a converter for older Zs values.

**Highlights:** 100% BS 7671 Zs Values, 80% On Site Guide Zs Values, Adjustable disconnection times (0.4s, 0.2s, 5s), BS EN Device Zs calculation, MCCB 60947-2 Zs charts, Zs Converter for 18th edition

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### Grant TechBox

[App page](https://appshunter.io/ios/app/grant-techbox/id1042420332)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Max Zs Values free?

Max Zs Values costs $9.99, with no in-app purchases.

### Is Grant TechBox free?

Grant TechBox is free to download, with no in-app purchases.

### Do Max Zs Values or Grant TechBox have ads?

Neither Max Zs Values nor Grant TechBox shows ads.

### Which is updated more often, Max Zs Values or Grant TechBox?

Max Zs Values ships an update every 4 months, and Grant TechBox every 12 months. Most recently, Max Zs Values was updated on September 24, 2026 and Grant TechBox on September 3, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*